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Arxiv.org
by Szymon Grabowski; Marcin Raniszewski
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Sampling (evenly) the suffixes from the suffix array is an old idea trading the pattern search time for reduced index space. A few years ago Claude et al. showed an alphabet sampling scheme allowing for more efficient pattern searches compared to the sparse suffix array, for long enough patterns. A drawback of their approach is the requirement that sought patterns need to contain at least one character from the chosen subalphabet. In this work we propose an alternative suffix sampling approach...
Topics: Data Structures and Algorithms, Computing Research Repository
Source: http://arxiv.org/abs/1406.2348
Arxiv.org
by John E. Ward; Javier Rico; Tarek Hassan; for the CTA Consortium
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The Cherenkov Telescope Array (CTA) is a future ground-based observatory (with two locations, in the Northern and Southern Hemispheres) that will be used in the study of the very-high-energy gamma-ray sky. CTA observations will be proposed by external users or initiated by the observatory, with the resulting measurements being processed by the CTA observatory and the reduced data made accessible to the corresponding proposer. Instrument Response Functions (IRFs) will also be provided to convert...
Topics: Instrumentation and Methods for Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1508.07437
Arxiv.org
by V. Stamatescu; Y. Becherini; K. Bernllöhr; E. Carmona; P. Colin; C. Farnier; L. Gerard; J. A. Hinton; B. Khélifi; N. Komin; G. Lamanna; J. -P. Lenain; G. Maier; A. Moralejo; C. L. Naumann; R. D. Parsons; F. Di Pierro; H. Prokoph; S. Vorobiov; for the CTA Consortium
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The Cherenkov Telescope Array (CTA) is a future instrument for very-high-energy (VHE) gamma-ray astronomy that is expected to deliver an order of magnitude improvement in sensitivity over existing instruments. In order to meet the physics goals of CTA in a cost-effective way, Monte Carlo simulations of the telescope array are used in its design. Specifically, we simulate large arrays comprising numerous large-size, medium-size and small-size telescopes whose configuration parameters are chosen...
Source: http://arxiv.org/abs/1211.3856v1
Defense Technical Information Archive
by Defense Technical Information Center
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Present procedures are inadequate for characterizing the radiation hardness of gate array product lines prior to personalization because the selection of circuits to be used, from among all those available in the manufacturer's circuit library, is usually uncontrolled. (Some circuits are fundamentally more radiation resistant than others.) In such cases, differences in hardness can result between different designs of the same logic function. Hardness also varies because many gate arrays feature...
Topics: DTIC Archive, Spratt, James P, FULL CIRCLE RESEARCH INC SAN MARCOS CA, *ARRAYS, *GATES(CIRCUITS),...
Defense Technical Information Archive
by Defense Technical Information Center
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Flush mounted slot antenna systems on metallic cones or ogival surfaces can be inertialessly scanned in the required direction. Since scanning over a wide angular region is generally desired, the radiation characteristics, including the effect of mutual coupling on the radiating elements, must be investigated before the more detailed system aspects are considered. To this end, various approximation techniques have been examined for use in pattern calculations and in impedance calculations....
Topics: DTIC Archive, Bargeliotes,Peter C, HUGHES AIRCRAFT CO CULVER CITY CALIF ANTENNA DEPT, *RADAR...
Defense Technical Information Archive
by Defense Technical Information Center
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The report presents the results of a study of the effectiveness of the experimental Large Aperture Seismic Array in Montana. An attempt has been made, where possible, to draw conclusions from the study of this one station about the performance that might be expected from a worldwide net of several of them. The report discusses the reliability and continuity of observations obtainable from a LASA system, the threshold level for automatic detection and location of weak events, the various...
Topics: DTIC Archive, MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB, *SEISMOMETERS, DETECTION,...
Defense Technical Information Archive
by Defense Technical Information Center
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A procedure is described which permits the computation of the radiation characteristics of a transducer array given the electrical inputs to the transducer elements. The effects of transducer element interactions (acoustic coupling) and dome-transducer interactions are included in the computation. The dome-transducer configuration chosen for this study is a rectangular array of circular elements mounted in a spherical baffle. This array is surrounded by a concentric, homogeneous dome. Numerical...
Topics: DTIC Archive, Moyer, W C, TRACOR INC AUSTIN TX, *SONAR ARRAYS, *TRANSDUCERS, *SONAR DOMES,...
Defense Technical Information Archive
by Defense Technical Information Center
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This report considers an array of reactively loaded aperture antennas, specifically, an N element array of closely-spaced waveguide-backed rectangular slots. Only the center waveguide is fed and the other waveguides are short circuited to provide the reactive loads. The positions of the short circuits are chosen to obtain maximum antenna gain in some specified direction. By varying the positions of the short circuits a directive beam can be steered through 180 deg. space. Both seven and nine...
Topics: DTIC Archive, Luzwick,John, Harrington,Roger F, SYRACUSE UNIV N Y DEPT OF ELECTRICAL AND COMPUTER...
Defense Technical Information Archive
by Defense Technical Information Center
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The effects of acoustic coupling between radiators is investigated for linear and planar acoustic arrays. To provide a simple model for calculation and inversion of the acoustic impedance matrices, spherical radiators are chosen. Considerations of total radiated beam power are addressed. The principal effect of element interaction on array performance found is in the effective impedance of individual radiators in the array. Keywords: Acoustic arrays; Linear arrays; Acoustic impedance; Acoustic...
Topics: DTIC Archive, Watson, K, MITRE CORP MCLEAN VA JASON PROGRAM OFFICE, *ACOUSTIC ARRAYS, *LINEAR...
Defense Technical Information Archive
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The performance of an array of hydrophones is determined by its response to the signal and noise fields in which it operates. This paper investigates the theoretical response of a vertical line array to the signal field in shallow water, taking the noise field as isotropic. A normal-mode propagation model was used to provide the incident field. Two methods of combining hydrophone signals have been studied: a broadside beamforming approach and a mode-matching method. In the first, limitations to...
Topics: DTIC Archive, Hamson,Rachel M, SACLANT ASW RESEARCH CENTRE LA SPEZIA (ITALY), *SONAR SOUND...
Arxiv.org
by Oleg L. Berman; Godfrey Gumbs; P. M. Echenique
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We calculate the low-frequency magnetoplasmon excitation spectrum for a square array of quantum dots on a two-dimensional (2D) graphene layer. The confining potential is linear in the distance from the center of the quantum dot. The electron eigenstates in a magnetic field and confining potential are mapped onto a 2D plane of electron-hole pairs in an effective magnetic field without any confinement. The tight-binding model for the array of quantum dots leads to a wavefunction with inter-dot...
Source: http://arxiv.org/abs/0901.1131v1
Arxiv.org
by M. Lacy; G. Wilson; F. Masci; L. J. Storrie-Lombardi; P. N. Appleton; L. Armus; S. C. Chapman; P. I. Choi; D. Fadda; F. Fang; D. T. Frayer; I. Heinrichsen; G. Helou; M. Im; S. Laine; F. R. Marleau; D. L. Shupe; B. T. Soifer; G. K. Squires; J. Surace; H. I. Teplitz; L. Yan
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We present Infrared Array Camera (IRAC) data and source catalogs from the Spitzer Space Telescope Extragalactic First Look Survey. The data were taken in four broad bands centered at nominal wavelengths of 3.6, 4.5, 5.8 and 8.0 microns. A set of mosaics and catalogs have been produced which are ~80% complete and ~99% reliable to their chosen flux density limits. The main field survey covers 3.8 deg^2, and has flux density limits of 20muJy, 25muJy, 100muJy and 100muJy at wavelengths of 3.6, 4.5,...
Source: http://arxiv.org/abs/astro-ph/0507143v1
Arxiv.org
by Hannes Jensen; Dainis Dravins; Stephan LeBohec; Paul D. Nuñez
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Kilometric-scale optical imagers seem feasible to realize by intensity interferometry, using telescopes primarily erected for measuring Cherenkov light induced by gamma rays. Planned arrays envision 50--100 telescopes, distributed over some 1--4 km$^2$. Although array layouts and telescope sizes will primarily be chosen for gamma-ray observations, also their interferometric performance may be optimized. Observations of stellar objects were numerically simulated for different array geometries,...
Source: http://arxiv.org/abs/1009.5828v1
The solar array drive mechanism for the Space Telescope embodies several features not customarily found on solar array drives. Power and signal transfer is achieved by means of a flexible wire harness for which the chosen solution, consisting of 168 standard wires, is described. The torque performance data of the harness over its temperature range are presented. The off load system which protects the bearings from the launch loads is released by a trigger made from Nitinol, the memory alloy....
Topics: NASA Technical Reports Server (NTRS), HARNESSES, HUBBLE SPACE TELESCOPE, MECHANICAL DRIVES, SOLAR...
NASA Network Resource and Training Site
by NASA Technical Reports Server (NTRS)
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The large number of radiation types composing the atmospheric radiation requires a complicated combination of instrument types to fully characterize the environment. A completely satisfactory combination has not as yet been flown and would require a large capital outlay to develop. In that the funds of the current project were limited to essential integration costs, an international collaboration was formed with partners from six countries and fourteen different institutions with their own...
Topics: NASA Technical Reports Server (NTRS), ATMOSPHERIC RADIATION, IONIZING RADIATION, FLIGHT...
Defense Technical Information Archive
by Defense Technical Information Center
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Wavenumber-frequency calibration of underwater, planar, receiving arrays requires the ability to generate single-wavenumber pressure fields over the surface of the array. When the wavenumber-frequency region of interest is evanescent, transmitting arrays previously constructed have been found to generate fields contaminated with harmonics, acoustic wavenumbers, and nonacoustic wavenumbers from the excitation of the antisymmetric Lamb waves. An array that greatly reduces contamination has...
Topics: DTIC Archive, Trivett, D H, NAVAL RESEARCH LAB ORLANDO FL UNDERWATER SOUND REFERENCE DETACHMENT,...
Automatic cuers and recognizers have been included in many recent weapons systems designs. In systems such as the Comanche helicopter a successful cuer/recognizer will significantly reduce crew workloads and will shorten acquisition timelines considerably. Focal plane array development has matured to the point where a new generation of common detector modules are being built under the IRFPA program. In the initial phases of the program it became important to take a look at different proposed...
Topics: DTIC Archive, Goodman, Daniel, CENTER FOR NIGHT VISION AND ELECTRO-OPTICS FORT BELVOIR VA, *FORWARD...
This thesis focuses on a Software Defined Radio (SDR) designed to compress a wideband radio signal input for a narrowband signal output. The design is based on a Field Programmable Gate Array (FPGA), which is chosen for its reprogrammability, flexibility, and our ability to introduce fault tolerance into the design. Software design tools allowed programming to be done at a high level, thereby allowing more progress on the design. This thesis focuses on one such SDR that was designed at a high...
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *RADIO SIGNALS, *SPACE ENVIRONMENTS, *FIELD...
This thesis focuses on a Software Defined Radio (SDR) designed to compress a wideband radio signal input for a narrowband signal output. The design is based on a Field Programmable Gate Array (FPGA), which is chosen for its reprogrammability, flexibility, and our ability to introduce fault tolerance into the design. Software design tools allowed programming to be done at a high level, thereby allowing more progress on the design. This thesis focuses on one such SDR that was designed at a high...
Topics: Algorithms, Electrical engineering, Software radio, Space environment
Arxiv.org
by W. L. Holzapfel; J. E. Carlstrom; L. Grego; G. Holder; M. Joy; E. D. Reese
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We have used the Berkeley-Illinois-Maryland-Association (BIMA) millimeter array outfitted with sensitive cm-wave receivers to search for Cosmic Microwave Background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration which produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is 6.6 arcminutes. We have made sensitive images of seven...
Source: http://arxiv.org/abs/astro-ph/9912010v1
Defense Technical Information Archive
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The purpose of this study was to establish the performance requirements for an airborne synthetic-array-radar (SAR) display and investigate the feasibility of meeting these requirements with a reflective display mechanization. A reflective liquid crystal display was chosen as the baseline mechanization to be evaluated with respect to its operational performance, fabrication feasibility and cost effectiveness. A set of performance requirements were established from psychophysical considerations...
Topics: DTIC Archive, Ernstoff, M N, HUGHES AIRCRAFT CO CULVER CITY CA, *SYNTHETIC APERTURE RADAR, *RADAR...
ANTIC Podcast Extras Collection
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Novel array representation methods in support of a microcomputer-based APL interpreter. Rochester Institute of Technology Abstract Objective: To study novel ways of representing data arrays for potential application in a microcomputer-based APL interpreter. The goal is to find, for arrays containing mixed integers and real numbers, a way to improve both storage efficiency and thruput, over that obtainable using conventional APL interpreter array representations. Investigation: For the purposes...
Topics: Rochester Institute of Technology, thesis, 6502 assembly language, Atari BASIC, APL programming...
This thesis investigated the EM scattering of a geodesic array consisting of a cluster of 20 trihedral corner reflectors held together by hinges. This target was designed to provide a large radar return with a spatial coverage greater than that due to an array of 8 corner reflectors. RCS, or echo area, was chosen as a means of investigating the EM scattering of a scaled model version of geodesic array. The RCS of the individual components of the geodesic array (i.e. the single corner...
Topics: DTIC Archive, Hamilton, Richard E, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...
Arxiv.org
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We discuss the detection of redshifted line and continuum emission at radio wavelengths using a Square Kilometer Array (SKA), specifically from low-excitation rotational molecular line transitions of CO and HCN (molecular lines), the recombination radiation from atomic transitions in almost-ionized hydrogen (radio recombination lines; RRLs), OH and water maser lines, as well as from synchrotron and free-free continuum radiation and HI 21-cm line radiation. The detection of radio lines with the...
Source: http://arxiv.org/abs/astro-ph/0409310v1
Defense Technical Information Archive
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The design, modeling, and performance measurements of a high frequency (HF) linear antenna array with 36 sensors is reported. The array was designed to achieve a narrow azimuthal beamwidth while maintaining grating lobes 10 dB below the main beam during a + or - 30 deg scan in azimuth. The configuration chosen utilizes two active vertical monopole elements and two parasitic backpoles to form a subarray. The subarrays, or sensors, are spaced at distances greater than half a wavelength to provide...
Topics: DTIC Archive, Gould, Anthony J, ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY, *IONOSPHERE, *ANTENNA...
Defense Technical Information Archive
by Defense Technical Information Center
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The work performed under this contract was related to the testing and procurement of the phase and, in particular, frequency processor boards that are needed in Trex Enterprises' second generation real-time passive millimeter-wave camera (PMC). In addition, an imaging demonstration performed under this contract demonstrated the feasibility of building such a PMC and that it is possible to obtain near diffraction limited imagery. The Trex Enterprises Corporation's PMC imager uses a patented flat...
Topics: DTIC Archive, Clark, Stuart, TREX ENTERPRISES SAN DIEGO CA, *MILLIMETER WAVES, *RADIOMETERS, *FOCAL...
Arxiv.org
by Massimo Tinto; Jose C. N. de Araujo; Helio K. Kuga; Marcio E. S. Alves; Odylio D. Aguiar
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We analyze the trajectories of three geostationary satellites forming the GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\cite{tinto}, a space-based laser interferometer mission aiming to detect and study gravitational radiation in the ($10^{-4} - 10$) Hz band. The combined effects of the gravity fields of the Earth, the Sun and the Moon make the three satellites deviate from their nominally stationary, equatorial and equilateral configuration. Since changes in the satellites...
Topics: Instrumentation and Methods for Astrophysics, Astrophysics, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1410.3023
Defense Technical Information Archive
by Defense Technical Information Center
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A theoretical Wiener multichannel filter was designed and applied to all operating subarrays for 14 noise samples and three signals. The filter system chosen had a disk signal model (11 km/sec to infinite velocity) and a noise annulus (2 to 6 km/sec) and exhibited good wavenumber response to 0.2 cps. Preliminary analysis showed that it was necessary to equalize the noise at the low-frequency peak (0.2 to 0.3 cps) prior to processing to obtain consistent noise rejection at low frequency. Because...
Topics: DTIC Archive, Harley, Terence W, TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV, *SEISMOMETERS,...
Naval Postgraduate School
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The electrical power subsystem is one of the most important elements of any satellite. This system must provide the necessary power to enable the payload and other subsystems to perform their functions. Once spacecraft requirements are determined and an electrical power subsystem is chosen; extensive testing is required to ensure power subsystem performance. Testing of CubeSat Kit compatible power systems is especially difficult due to the inaccessibility of test points. This thesis concerns...
Topics: Space vehicles, Engineering
The electrical power subsystem is one of the most important elements of any satellite. This system must provide the necessary power to enable the payload and other subsystems to perform their functions. Once spacecraft requirements are determined and an electrical power subsystem is chosen; extensive testing is required to ensure power subsystem performance. Testing of CubeSat Kit compatible power systems is especially difficult due to the inaccessibility of test points. This thesis concerns...
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *SOLAR CELLS, *ELECTRIC POWER, THESES, TEST...
We examine how rectangular array model can support students' spatial structuring in learning multiplication. To begin, we define what we mean by spatial structuring as the mental operation of constructing an organization or form for an object or set of objects. For that reason, the eggs problem was chosen as the starting point in which the students could recognize such an arrangement. Geoboard was also be used as a tool to visualize the array. This research focused on a design research that was...
Topics: ERIC Archive, Foreign Countries, Elementary School Students, Elementary School Mathematics,...
Arxiv.org
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Although the relationship between the far-infrared and cm-wave radio luminosities of normal galaxies is one of the most striking correlations in astronomy, a solid understanding of its physical basis is lacking. In one interpretation, the "calorimeter model," rapid synchrotron cooling of cosmic ray electrons is essential in reproducing the observed linear relationship. Observed radio spectra, however, are shallower than what is expected of cooled synchrotron emission. In Thompson et...
Source: http://arxiv.org/abs/0912.0014v1
From September through November the author concentrated on the development of an Integrated Image Understanding Benchmark for computer vision architectures. Unlike previous vision benchmarks, this new benchmark is designed to test machine performance on a complete interpretation task. The task chosen will require not only that common low-level vision operations be performed, but that intermediate-level operations and interactions between operations be tested as well. In fact, the emphasis of...
Topics: DTIC Archive, Riseman, Edward, MASSACHUSETTS UNIV AMHERST, *IMAGE PROCESSING, *PARALLEL PROCESSING,...
This project is involved performing a siting survey for an advanced seismic array in the FRG which could be used in a multi-array network jointly with arrays in Scandinavia to detect and identify seismic events especially at regional distances. To assess the eventual capabilities of a new high-frequency array it was necessary not only to conduct a noise survey but also to determine signal coherence in an area corresponding to the array aperture. After an extensive field survey, the Bavarian...
Topics: DTIC Archive, Harjes, H -P, BOCHUM UNIV (GERMANY F R), *NOISE, *SEISMIC ARRAYS, MEASUREMENT,...
Arxiv.org
by L. Van Look; S. Raedts; R. Jonckheere; V. V. Moshchalkov
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We investigate anisotropy in the vortex pinning in thin superconducting films with a square array of rectangular submicron holes ("antidots"). The size of the antidots is chosen in such a way that it corresponds to a saturation number n_s=1, i.e. each antidot can trap at most one flux quantum. Therefore, interstitial vortices, appearing when the magnetic field exceeds the first matching field, are "caged" at the interstitial positions by the repulsion from the saturated...
Source: http://arxiv.org/abs/cond-mat/0302252v1
Arxiv.org
by P. A. Henning; C. M. Springob; R. F. Minchin; E. Momjian; B. Catinella; T. McIntyre; F. Day; E. Muller; B. Koribalski; J. L. Rosenberg; S. Schneider; L. Staveley-Smith; W. van Driel
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The Arecibo L-band Feed Array (ALFA) is being used to conduct a low-Galactic latitude survey, to map the distribution of galaxies and large-scale structures behind the Milky Way through detection of galaxies' neutral hydrogen (HI) 21-cm emission. This Zone of Avoidance (ZOA) survey finds new HI galaxies which lie hidden behind the Milky Way, and also provides redshifts for partially-obscured galaxies known at other wavelengths. Before the commencement of the full survey, two low-latitude...
Source: http://arxiv.org/abs/1002.2933v1
Defense Technical Information Archive
by Defense Technical Information Center
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This report describes work performed due to ESA contract No. 101 34/ 93/NL/PB. Started is with a literature study on dual polarised waveguide radiators, resulting in the choice for the open ended square waveguide. After a thorough description of the mode matching infinite waveguide array analysis method - including finiteness effects - , that forms the basis for all further described analysis and synthesis methods, the accuracy of the analysis software is validated by comparison with...
Topics: DTIC Archive, Visser, H J, FYSISCH EN ELEKTRONISCH LAB TNO THE HAGUE (NETHERLANDS), *WAVEGUIDES,...
The transmission of large amounts of power in space by laser beam (diode lasers, in particular) requires an array of lasers to increase total power. Concentration of the beam requires some degree of coherence. Temporal coherence can be obtained by locking amplifiers to a master oscillator. However, spatial coherence is not so easily created or maintained. Many mechanical, thermal, and electrical factors oppose it continually. A very simple method is described for creating and maintaining a...
Topics: NASA Technical Reports Server (NTRS), LASER ARRAYS, LASER BEAMS, PHASED ARRAYS, SEMICONDUCTOR...
Defense Technical Information Archive
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A preliminary simulation model of the search mode of a phased array radar has been developed. The basic components are a search strategy for the radar, an evasion policy for the target, and a simple radar environment. At present there is no attempt at adaptive modification of either component. A particular search strategy has been chosen. There is provision in the simulator to modify the procedure, however. The evasion policy of the target is one of changing course at random times with random...
Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC, *COMPUTER PROGRAMS, *PHASED ARRAYS, *RADAR TARGET...
Defense Technical Information Archive
by Defense Technical Information Center
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Aircraft navigation imposes critical speed requirements on the embedded avionics processor, requirements which will become even more rigorous in the future as additional, increasingly sophisticated navigation data becomes available in the cockpit. The fusion of navigation sensor data to arrive at an accurate position determination is done using a programmed algorithm called a Kalman filter. Achieving the necessary processing speed for next-generation navigation filters will require the use of...
Topics: DTIC Archive, Dudzinski,Edward C, AIR FORCE WRIGHT AERONAUTICAL LABS WRIGHT-PATTERSON AFB OH,...
Arxiv.org
by Jie-Qiao Liao; Z. R. Gong; Lan Zhou; Yu-xi Liu; C. P. Sun; Franco Nori
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We theoretically study how to control transport, bound states, and resonant states of a single photon in a one-dimensional coupled-cavity array. We find that the transport of a single photon in the cavity array can be controlled by tuning the frequency of either one or two cavities. If one of the cavities in the array has a tunable frequency, and its frequency is tuned to be larger (or smaller) than those of other cavities, then there is a photon bound state above (or below) the energy band of...
Source: http://arxiv.org/abs/0909.2748v3
A tent shaped PV array was designed and the design was optimized for maximum specific power. In order to minimize output power variation a tent angle of 60 deg was chosen. Based on the chosen tent angle an array structure was designed. The design considerations were minimal deployment time, high reliability, and small stowage volume. To meet these considerations the array was chosen to be self-deployable, form a compact storage configuration, using a passive pressurized gas deployment...
Topics: NASA Technical Reports Server (NTRS), DEPLOYMENT, DESIGN ANALYSIS, FOLDING STRUCTURES, FUNCTIONAL...
Phased-array antenna systems offer many advantages to low-Earth-orbiting satellite systems. Their large scan angles and multibeam capabilities allow for vibration-free, rapid beam scanning and graceful degradation operation for high rate downlink of data to users on the ground. Technology advancements continue to reduce the power, weight, and cost of these systems to make phased arrays a competitive alternative in comparison to the gimbled reflector system commonly used in science missions. One...
Topics: NASA Technical Reports Server (NTRS), PHASED ARRAYS, MICROWAVE ANTENNAS, ANTENNA ARRAYS, ANTENNA...
In radiometer applications, it is required to design antennas that meet low average sidelobe levels and low average return loss over a specified frequency bandwidth. It is a challenge to meet such specifications over a frequency range when one uses resonant elements such as waveguide feed slots. In addition to their inherent narrow frequency band performance, the problem is exacerbated due to modeling errors and manufacturing tolerances. There was a need to develop a design methodology to solve...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, GENETIC ALGORITHMS, ITERATION, RADIOMETERS,...
The objectives of this project are: (1) To investigate the limits of empirical matched field processing and other coherent array detection and parameter estimation methods as receiver aperture size increases from a few kilometers to many hundreds of kilometers. (2) To investigate techniques for extending the geographical source-region footprint over which empirical matched field processing and other coherent calibrated methods apply. Under a previous contract, we demonstrated the ability of...
Topics: DTIC Archive, Ringdal, Frode, NORWEGIAN SEISMIC ARRAY (NORSAR) KJELLER, *PROCESSING, *APERTURES,...
Defense Technical Information Archive
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This Interim Report presents the results of studies leading to the design of a cylindrical lens-array antenna for two-dimensional electronic scanning when the signal has a wide instantaneous bandwidth. The constant-path cylindrical lens defined by Rotman and Franchi is studied for contours, phase aberrations, amplitude distortions, and surface incidence angles. One form of this lens is the R-2R lens, which is chosen for this project. Design of the antenna for low sidelobes is considered. In...
Topics: DTIC Archive, Hannan,P W, HAZELTINE CORP GREENLAWN NY, *Antenna arrays, *Lens antennas, *Sidelobes,...
It is now possible to grow silicon nanowires at chosen positions and orientations by a method that involves a combination of standard microfabrication processes. Because their positions and orientations can be chosen with unprecedented precision, the nanowires can be utilized as integral parts of individually electronically addressable devices in dense arrays. Nanowires made from silicon and perhaps other semiconductors hold substantial promise for integration into highly miniaturized sensors,...
Topics: NASA Technical Reports Server (NTRS), SEMICONDUCTORS (MATERIALS), SILICON DIOXIDE, NANOWIRES,...
Arxiv.org
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The electrical properties of a set of seven-helix transmembrane proteins, whose space arrangement (3D structure) is known, are investigated by using regular arrays of the amino acids. These structures, specifically cubes, have topological features similar to those shown by the chosen proteins. The theoretical results show a good agreement between the predicted current-voltage characteristics obtained from a cubic array and those obtained from a detailed 3D structure. The agreement is confirmed...
Topics: Quantitative Biology, Materials Science, Quantitative Methods, Soft Condensed Matter, Physics,...
Source: http://arxiv.org/abs/1507.07691
Defense Technical Information Archive
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The requirement for increased gas turbine engine performance has led to the use of much higher turbine entry temperature (TET). The higher temperatures require active cooling of the turbine blade using compressor bleed air. Arrays of impinging jets are one method currently used to reduce the blade temperature on the midspan and leading edge. Air flows through small holes in a blade insert and is directed on the inside surface of a turbine blade to reduce local surface temperature. The engine...
Topics: DTIC Archive, Van Treuren, Kenneth W, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH, *TURBINE...
The Kuiper Widefield Infrared Camera (KWIC) is an imaging spectrometer designed for use on the Kuiper Airborne Observator between 18 and 40 microns. The spectral resolution achieving devices are two fully tunable and scanning cryogenic Fabry-Perot interferometers that employ free standing metal mesh as the reflective surfaces. The detective device is a 128 x 128 pixel Si:Sb BIB array manufactured by Rockwell/Boeing for the SIRTF project. The plate scale for KWIC (one pixel subtends 2.73" x...
Topics: NASA Technical Reports Server (NTRS), IMAGING SPECTROMETERS, INFRARED RADIATION, CAMERAS, SPECTRAL...
Defense Technical Information Archive
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The use of sensors configured into various geometrical shapes called arrays are important in extracting signal information in many applications. This paper explores the effectiveness of a two-dimensional or planar array in extracting signal information from digitized data when additive Gaussian noise and additive impulsive interference are present. Based on the likelihood ratio approach the data output of each sensor is first passed through a zero-memory device. The zero-memory device is...
Topics: DTIC Archive, Dwyer,Roger F, NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON LAB, *DIGITAL...
Arxiv.org
by Y. Jompol; C. J. B. Ford; I. Farrer; G. A. C. Jones; D. Anderson; D. A. Ritchie; T. W. Silk; A. J. Schofield
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We present the results of non-linear tunnelling spectroscopy between an array of independent quantum wires and an adjacent two-dimensional electron gas (2DEG) in a double-quantum-well structure. The two layers are separately contacted using a surface-gate scheme, and the wires are all very regular, with dimensions chosen carefully so that there is minimal modulation of the 2DEG by the gates defining the wires. We have mapped the dispersion spectrum of the 1D wires down to the depletion of the...
Source: http://arxiv.org/abs/0708.0267v2
Arxiv.org
by Jonathan P. Jacky; Joseph L. Garbini; Matthew Ettus; John A. Sidles
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This report describes a cantilever controller for magnetic resonance force microscopy (MRFM) based on a field programmable gate array (FPGA), along with the hardware and software used to integrate the controller into an experiment. The controller is assembled from a low-cost commercially available software defined radio (SDR) device and libraries of open-source software. The controller includes a digital filter comprising two cascaded second-order sections ("biquads"), which together...
Source: http://arxiv.org/abs/0809.1403v1
The algorithm for quadratic global optimization performed by a cellular neural network (CNN) with a slowly varying slope of the output characteristic is analyzed. It is shown that the only CNN which finds the global minimum of a quadratic function for any values of the input parameters is the network composed by only two cells. If the dimension is higher than two, even the CNN described by the simplest one-dimensional space-invariant template A=A(exp 1), A (exp 0), A (exp 1), fails to find the...
Topics: DTIC Archive, Chua, Leon O, CALIFORNIA UNIV BERKELEY, *NEURAL NETS, *CHIPS(ELECTRONICS),...
A brief summary of neural networks is presented which concentrates on the design constraints imposed. Major design issues are discussed together with analysis methods and the chosen solutions. Although the system will be capable of running on most transputer architectures, it currently is being implemented on a 40-transputer system connected to a toroidal architecture. Predictions show a performance level equivalent to that of a highly optimized simulator running on the SX-2 supercomputer.
Topics: NASA Technical Reports Server (NTRS), ARCHITECTURE (COMPUTERS), ARTIFICIAL INTELLIGENCE,...
Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with...
Topics: NASA Technical Reports Server (NTRS), MICROWAVE ANTENNAS, SATELLITE COMMUNICATION, ANTENNA ARRAYS,...
A study of various aspects of Adjustable Speed Drives (ASD) is presented. A summary of the relative merits of different ASD systems presently in vogue is discussed. The advantages of using microcomputer based ASDs is now widely understood and accepted. Of the three most popular drive systems, namely the Induction Motor Drive, Switched Reluctance Motor Drive and Brushless DC Motor Drive, any one may be chosen. The choice would depend on the nature of the application and its requirements. The...
Topics: NASA Technical Reports Server (NTRS), COMPUTERIZED SIMULATION, MECHANICAL DRIVES, INDUCTION MOTORS,...
Arxiv.org
by Olivier Richoux; Agnès Maurel; Vincent Pagneux
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In this paper, the influence of disorder on 1D periodic lattice of resonant scatterers is inspected. These later have multiple resonance frequencies which produce bandgap in the transmission spectrum. One peculiarity of the presented system is that it is chosen with a nearly perfect overlap between the Bragg and the second hybridization bandgaps. In the case of a perfect ordered lattice, and around this overlap, this produces a narrow transparency band within a large second bandgap. As...
Topics: Physics, Mesoscale and Nanoscale Physics, Optics, Condensed Matter
Source: http://arxiv.org/abs/1410.1871
Defense Technical Information Archive
by Defense Technical Information Center
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Autonomous MAC and ALU processors and register files (three types of Silicon Objects) are implemented with custom logic to achieve 1GHz fixed-point multiply and accumulate. Synchronous programmable interconnect and embedded storage reduces the need for difficult index calculation and the use of external memory for intermediate values. The flexibility of the objects and their interconnect allows the level of parallelism to be chosen freely based on performance requirements and resource...
Topics: DTIC Archive, Helgemo, Dirk R, MATHSTAR INC MINNEAPOLIS MN, *SIGNAL PROCESSING, *ARRAYS, *PARALLEL...
This work addresses the problem of excitation of a parallel plate waveguide by an array of rectangular waveguides that arises in applications such as the continuous transverse stub (CTS) antenna and dual-polarized parabolic cylindrical reflector antennas excited by a scanning line source. In order to design the junction region between the parallel plate waveguide and the linear array of rectangular waveguides, waveguide sizes have to be chosen so that the input match is adequate for the range...
Topics: NASA Technical Reports Server (NTRS), RECTANGULAR WAVEGUIDES, PARALLEL PLATES, CYLINDRICAL...
PubMed Central
by Wee, F. H.; Malek, F.; Al-Amani, A. U.; Ghani, Farid
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This article is from Scientific Reports , volume 4 . Abstract The microwave industry has shown increasing interest in electronic ceramic material (ECM) due to its advantages, such as light weight, low cost, low loss, and high dielectric strength. In this paper, simple antennas covered by superstrate layers for 2.30 GHz to 2.50 GHz are proposed. The antennas are compact and have the capability of producing high performance in terms of gain, directivity, and radiation efficiency. Bismuth...
Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3892718
Defense Technical Information Archive
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The ambient seismic noise at LASA was studied using high-resolution wavenumber spectra obtained for several subarrays chosen from seven noise samples covering a seven month period. A comparision of the high-resolution spectra with conventional spectra measured at two subarrays for one of the noise samples was made. Estimations of the frequency power spectra of the mantle P- wave noise and isotropic Rayleigh-wave energy were obtained. Also, estimations of the power spectra were determined for...
Topics: DTIC Archive, Crouch, Donald B, TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV, *NOISE,...
Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, STANDING WAVES, WAVEGUIDES, PLANAR...
Arxiv.org
by V. Filinov; P. Thomas; I. Varga; T. Meier; M. Bonitz; V. Fortov; S. W. Koch
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The quantum dynamics of an ensemble of interacting electrons in an array of random scatterers is treated using a new numerical approach for the calculation of average values of quantum operators and time correlation functions in the Wigner representation. The Fourier transform of the product of matrix elements of the dynamic propagators obeys an integral Wigner-Liouville-type equation. Initial conditions for this equation are given by the Fourier transform of the Wiener path integral...
Source: http://arxiv.org/abs/cond-mat/0203585v1
Solar array candidate configurations (flexible rollup, flexible flat-pact, semi-rigid panel, semi-rigid flat-pack) were analyzed with particular attention to the specific power (W/kg) requirement. Two of these configurations (flexible rollup and flexible flat-pack) are capable of delivering specific powers equal to or exceeding the baseline requirement of 200 W/kg. Only the flexible rollup is capable of in-flight retraction and subsequent redeployment. The wrap-around contact photovoltaic cell...
Topics: NASA Technical Reports Server (NTRS), PHOTOVOLTAIC CELLS, SOLAR ARRAYS, SOLAR CELLS, AEROSPACE...
The port-side photovoltaic power module (P6) was activated on the International Space Station in December 2000. P6 provides electrical power to channels 2B and 4B to operate ISS power loads. A P6 is shown in the preceding photograph. This article highlights the work done at the NASA Glenn Research Center to calculate the on-orbit degradation of the P6 solar array wings (SAWs) using on-orbit data from December 2000 to February 2003. During early ISS operations, the 82 strings of photovoltaic...
Topics: NASA Technical Reports Server (NTRS), INTERNATIONAL SPACE STATION, SOLAR ARRAYS, PERFORMANCE TESTS,...
The radiating aperture of a circularly polarized, active electronically scanned array (AESA) that operates from 20 GHz to 60 GHz and scans up to 60 from broadside is reported. Design guidelines for wideband arrays are briefly reviewed, and the linearly-polarized connected Vivaldi array is chosen as the radiating element due to its simplicity in design and fabrication. Infinite array simulations are used to characterize the performance of a linear-to-circular polarizer placed on top of a...
Topics: DTIC Archive, Pfeiffer,Carl R, Defense Engineering Corporation Beavercreek United States,...
PubMed Central
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This article is from Sensors (Basel, Switzerland) , volume 14 . Abstract A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different...
Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4029633
PubMed Central
by Wang, Jiying; Jiang, Jicai; Wang, Haifei; Kang, Huimin; Zhang, Qin; Liu, Jian-Feng
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This article is from PLoS ONE , volume 9 . Abstract Copy number variations (CNVs) are important forms of genomic variation, and have attracted extensive attentions in humans as well as domestic animals. In the study, using a custom-designed 2.1 M array comparative genomic hybridization (aCGH), genome-wide CNVs were identified among 12 individuals from diverse pig breeds, including one Asian wild population, six Chinese indigenous breeds and two modern commercial breeds (Yorkshire and Landrace),...
Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3903766
Five short-period events were processed using a 15-sec gate for the LASA A0, D-ring subarray, a 10-sec gate for the extended E3 subarray, and a 5- sec gate for the F1 subarray. Gate positions were based on time-trace playbacks and were chosen to include the primary P-wave arrivals. For an event recorded on 21 June 1967 from eastern Russia or northeastern China, all f-k give a reasonable accurate location at the 'peak' frequency for this event; however, this is not true for all events. Three...
Topics: DTIC Archive, Binder, Frank H, TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV, *SEISMOLOGICAL...
Three major options for wide-scale generation of photovoltaic energy for terrestrial use are considered: (1) rooftop array, (2) solar farm, and (3) satellite station. The rooftop array would use solar cell arrays on the roofs of residential or commercial buildings; the solar farm would consist of large ground-based arrays, probably in arid areas with high insolation; and the satellite station would consist of an orbiting solar array, many square kilometers in area. The technology advancement...
Topics: NASA Technical Reports Server (NTRS), PHOTOVOLTAIC CONVERSION, SOLAR ARRAYS, SOLAR CELLS, DIRECT...
A study has been made of microwave amplifier modules designed for phased array antenna service. Output amplitude and phase behavior have been measured under mismatched load conditions at fundamental and harmonic frequencies. A bridge has been used that is capable of being balanced at fundamental, second and third harmonics. Reference signals at these frequencies are adjusted in amplitude and phase to cancel the corresponding components produced by the amplifier under test. The amplitude and...
Topics: DTIC Archive, Griffin,Donald W, SYRACUSE UNIV N Y DEPT OF ELECTRICAL AND COMPUTER ENGINEERING,...
The building of operational clear air radar wind profilers is discussed. The choice of operating frequency and antenna configuration for these profilers is examined. The cost and performance of a (10 lambda) 2 antenna array versus operating frequency over the range 30 to 400 MHz is compared. To simplify the comparison the array beam will be fixed and the array will be uniformly fed. Yagi and coaxial collinear (COCO) cable antennas are compared, although other configurations may be competitive....
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, ANTENNA RADIATION PATTERNS, PROFILOMETERS,...
Futuristic wireless communication systems must perform in environments that generate scattering from various obstacles which in turn cause multipath effects to be dominant. This results in degradation in the overall performance that can be avoided if the antennas have narrow beamwidths and low sidelobes. Advanced designs for Rapidly Deployable Radio Network (RDRN) systems are required to consider transmission at single frequency to several mobile users in a single frequency cell. This in turn...
Topics: DTIC Archive, Chatterjee, Deb, KANSAS UNIV CENTER FOR RESEARCH INC LAWRENCE TELECOMMUNICATIONS AND...
We present the results of a 5GHz survey with the Very Large Array (VLA) and the expanded VLA, designed to search for short-lived (approx < 1 day) transients and to characterize the variability of radio sources at milli-Jansky levels. A total sky area of 2.66 sq. deg, spread over 141 fields at low Galactic latitudes (b approx equals 6 - 8 deg) was observed 16 times with a cadence that was chosen to sample timescales of days, months and years. Most of the data were reduced, analyzed and...
Topics: NASA Technical Reports Server (NTRS), NEUTRON STARS, RADIO ASTRONOMY, RADIO STARS, VARIABLE STARS,...